Cerebrospinal fluid pressure in conscious head-down tilted rats.

Cerebrospinal fluid pressure (PCSF) was continuously measured in conscious male Sprague-Dawley rats gently restrained by a cotton towel. PCSF, evaluated in 15-min time blocks over a 3-h experiment, increased slightly (p less than 0.05) during the first 30 min of a control hour at 0 degree. There was a transient increase for about 5 min immediately after tilt (-45 degrees) that may have been due to head movement after the position change. However, PCSF was statistically unchanged (p greater than 0.05) during the 2nd (-45 degrees) hour and the 3rd (0 degree) recovery hour. The data show that the dynamics of intracranial pressure regulation can accommodate the acute cephalad fluid shift after tilting.